Dosimetric and physical comparison of IMRT and CyberKnife plans in the treatment of localized prostate cancer

OBJECTIVES: We aimed to conduct a retrospective dosimetric and physical comparison of CK (CyberKnife) and IMRT (intensity-modulated radiotherapy) plans in 16 prostate cancer cases. METHODS: For the comparison of IMRT and CK in 16 patients, CI (conformity index), HI (homogeneity index), and the 100% (V100), 66% (V66), 50% (V50), 33% (V33) and 10% (V10) doses received by rectum and bladder volumes were investigated. RESULTS: The doses of V10, V33 and V50 rectum volumes were found to be lower in CK (p<0.001, 0.001, and 0.019, respectively). Percentage doses of V66 and V100 volumes were higher in CK. Mean percentage doses received by V10 and V33 bladder volumes were found to be lower in CK. The percentage doses received by the V50 and V60 bladder volumes were 5.4% and 3.45% in IMRT and 13.4% and 8.05% in CK. Mean CI was 0.94 in IMRT and 1.23 in CK; HI was 1.08 in IMRT and 1.33 in CK (p<0.001). CONCLUSION: In the high-dose region, CK treatment was found to be superior to IMRT. Dose heterogeneity in target volume was lower in CK plans due to the properties of the system. While CI was better in IMRT, critical organ protection was better in CK.